Fossils from Australia. 159 



42. Modiolopsis siliqua. — Elongate, length nearly twice the height, 

 very inequilateral, enlarging a little posteriorly; front obliquely trun- 

 cate; anterior part less than a fourth whole length; dorsal margin 

 straight and nearly horizontal, inferior margin straight; lateral surface 

 flattened but not concave ; posterior surface rounded or scarcely cari- 

 nate near summit of beak ; surface marked with irregular obsolescent 

 plicae and showing also lines of growth. — Length 1£ inch ; height 

 (greatest) ^ L ; apical angle about 130°. Near Mytilus Teploji of 

 Verneuil, (Russia, pi. xix, 17,) and Modiolopsis f aba, of J. Hall, (N. Y. 

 PateooL Report, pi. xxxv, fig. 6.)—lllawarra. 



43. Modiolopsis prcerupta. — Elongate (length about twice the great- 

 est height), enlarging somewhat posteriorly, dorsal margin straight or 

 very slightly arcuate, rounding into the posterior margin ; inferior ex- 

 cavate anterior to middle ; front abruptly truncate ; lateral surface ex- 

 cavate from the beak posteriorly downward, also an oblique depression 

 adjoining anterior muscular impression ; a few faint rays from the beak 

 over the posterior surface, concentric striae of growth distinct; anterior 

 muscular impression marginal, excavate, but small and suborbicular, 

 —Length 1-^ inch ; greatest height T 5 ^ L ; apical angle 100°. 

 flear M. faba of Hall.— lllawarra. 



44. Modiolopsis imbricata. — Moderately elongate, enlarging poste- 

 riorly, very inequilateral ; dorsal margin straight, and prolonged ; infe- 

 rior mar gin straight anteriorly, front rounded ; lateral surface depressed 

 or somewhat excavate from the beak obliquely backward and down- 



iu, naving neat concentric subimbricate markings (and some fine 

 ra tations on the posterior surface of cast near beak) ; from beak to 

 posterior margin scarcely carinate ; anterior muscular impression very 

 ^ r S^ °Wong, marginal; beaks of cast thin at summit. Texture of 

 . ell delicately fibrous and apparently no nacre below.* — Length 2£ 

 lnches 5 greatest height about half the length.— Harper's Hill 

 • f Modiolopsis arcodes. — A thick species resembling the preceding 

 orm and in external markings ; but it is much broader in proportion, 

 j*teral surface is less flattened anteriorly, cardinal line much shorter 

 an shell, being much less prolonged posteriorly than in M. imbricata ; 

 jne from beak posteriorly more decidedly carinate, beaks thicker. 

 *" e fibrous texture is very distinct. The anterior muscular impression 

 ! s ve ry oblong vertically, and projects anterior to the beaks, nearly as 

 ,n the Myopkora of Bronn.— Length If inch; height much less than 

 half length. Looks much like an Area in general form.— Harper's 



mil. 



46. Modiolopsis acutifrons.— -Thick, elongate, very much broader 

 Posteriorly • cardinal line straight, very oblique, very much shorter than 

 she| l ; front acuminate, posterior broadly rounded ; inferior margin ex- 

 cavate near anterior extremity and also just posterior to beak ; lateral 

 surface from beak downward and backward excavate, from beak to pos- 

 terior margin very convex, hardly carinate ; surface marked with a few 

 c °ncentric folds, and some lines of growth. Anterior muscular impres- 



* Edging from this testure, the species of Modiolopsis (Hall) ■£ mow allied to 

 Areola than Mytilus, although having a large and strong anterior muscular im- 



Passion. 



